In Syrian peace talks this weekend, Russia will call for drafting a new constitution that would be voted on and followed by an early presidential election, according to a draft of the plan.

The draft plan makes no mention of Syrian President Bashar al-Assad stepping down during the transition -- a key demand of the West and Gulf states participating in the peace talks.

It only mentions that "the president of Syria will not chair the constitutional commission," but rather the reform process will be led by "a candidate agreed by all sides."

The plan calls for UN special Syrian envoy Staffan de Mistura to launch a political process between the Syrian government and "a united delegation of the opposition groups" on the basis of a communique issued by major powers in June 2012 that calls for setting up a transitional government leading to elections.

The transition period and constitutional reform process could take up to 18 months, the documents says.

"And, of course, we are receptive for proposals from the other side. It's just Russia's contribution, how we launch a political process...to make parties work together -- government and opposition," he said.

The document was circulated ahead of a second round of talks in Vienna on November 14 among key players on both sides of the Syrian conflict. De Mistura told reporters that he hopes the talks will not waste the "momentum" he currently sees building for peace.

At the first round of peace talks on October 30, the United States, Russia, Iran, and more than a dozen other nations agreed to launch a new peace effort, but they carefully avoided the divisive issue of when Assad might leave power -- a dispute at the heart of the conflict that has claimed more than 250,000 lives.

De Mistura said he hopes the second round will "bring some deliverables for the Syrian people, and one of them should be reduction of violence."

The Russian document, titled Approach To The Settlement of The Syrian Crisis, focuses on both opposition groups and "terrorist groups," and the need to differentiate between them.

It calls for the UN Security Council to list the Islamic State (IS) group as "terrorist" along with other groups which have not as yet been specified.

Russian Foreign Minister Sergei Lavrov said on November 10 that he hopes one of the outcomes of the upcoming negotiations will be agreement on which groups should be included on the terrorist list.

The Russian plan says IS and other designated terrorist groups would be excluded from any cease-fire declared in Syria.

Moscow has also said opposition groups must be designated for participation in the peace talks, and it has exchanged a list of 38 candidates with Saudi Arabia.

The Russian draft plan says groups which are included in the opposition delegation have to be agreed beforehand, and those included must show their "readiness...to share the goals of preventing terrorists from coming to power in Syria and of ensuring the sovereignty, territorial integrity, and political independence of Syria, as well as the secular and democratic character of the state."

Western diplomats who saw the Russian plan said it would be difficult for countries opposed to Assad to agree to it.

"The document does not suit a lot of people," one Western diplomat said, adding that those who disagreed with Russia's approach were working to make sure the text would not be the basis for the talks.

A second Western diplomat said Moscow wants to include all insurgent groups on the terrorist list unless they are battling IS and not battling the Syrian regime.